Light guide plate, planar light source apparatus, display apparatus, and electronic device

ABSTRACT

To provide a technique for suppressing brightness non-uniformity of an area illuminated by a light source and also suppressing a decline in contrast between areas caused by incidence of a luminous flux of the area to another area. Provided is a light guide plate including: a diverging portion which is provided on an opposite side of a light exit surface from which light is emitted, the diverging portion causing a luminous flux emitted from a light emitting element to diverge; and a restricting portion which is provided, when a prescribed range from the light emitting element on the light exit surface is defined as an illuminated area illuminated by the light emitting element, in at least a periphery of the illuminated area on the light exit surface and which deflects or shields light traveling from inside toward outside of the illuminated area to restrict traveling, toward a side of the light exit surface, of light traveling toward the outside of the illuminated area.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 16/339,726,filed on Apr. 5, 2019, which is a National Stage Application under 35USC § 371 of PCT International Application No. PCT/JP2017/043615, whichis based upon and claims the benefit of priority from the prior JapanesePatent Application No. 2016-246164, filed on Dec. 20, 2016, the entirecontents of all of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a light guide plate, a planar lightsource apparatus, a display apparatus, and an electronic device.

BACKGROUND ART

Backlight systems for liquid crystal display apparatuses include asystem referred to as an edge light-type backlight and a system referredto as a direct-type backlight. Direct-type backlights which feature highlight utilization efficiency and which enable higher brightness to bereadily achieved are used in displays of large-size liquid crystaldisplay apparatuses. In addition, for example, an LED (Light EmittingDiode) which emits white light is used as a light source of a backlight.In the case of a direct-type backlight, while a plurality of LEDs arearranged directly underneath a liquid crystal display apparatus,brightness non-uniformity easily occurs in the liquid crystal displayapparatus between portions directly above the LEDs and other portions.

Conventionally, a planar light source apparatus has been proposed inwhich a light source is installed in a conical depression for lightsource insertion provided on a rear surface of a light guide plate, andlight-scattering dots for scattering light inside the light guide plateare provided on the rear surface of the light guide plate, the planarlight source apparatus being configured so that at least a part of lightfrom the light source is first reflected by a front surface and/or therear surface of the light guide plate and subsequently emitted from thefront surface of the light guide plate (refer to PTL 1).

CITATION LIST Patent Literature

[Patent Document 1] Japanese Patent No. 3427636

SUMMARY OF INVENTION Technical Problem

In addition, in a direct-type backlight, a plurality of LEDs arearranged in a matrix pattern constituted by vertical columns andhorizontal rows on a surface directly underneath a display, andso-called local dimming may be performed in which light on/off of eachLED is controlled so as to partially change brightness of a displayregion based on data of an image displayed on the display.

When adjusting brightness for each area in which an LED is provided in abacklight performing local dimming, while a luminous flux from each LEDmust be diffused to suppress brightness non-uniformity on a displaysurface within the area in which the LED is provided, there is a problemin that leakage of the diffused luminous flux to another area causes adecline in contract between areas.

In consideration of such circumstances, an object of the presentinvention is to provide a technique for suppressing brightnessnon-uniformity of an area illuminated by a light source and alsosuppressing a decline in contrast between areas caused by incidence of aluminous flux of the area to another area.

Solution to Problem

In the present invention, the following means is adopted in order tosolve the problem described above. Specifically, a light guide plateaccording to the present invention includes: a diverging portion whichis provided on an opposite side of a light exit surface from which lightis emitted, the diverging portion causing a luminous flux emitted from alight emitting element to diverge; and a restricting portion which isprovided, when a prescribed range from the light emitting element on thelight exit surface is defined as an illuminated area illuminated by thelight emitting element, in at least a periphery of the illuminated areaon the light exit surface and which deflects or shields light travelingfrom inside toward outside of the illuminated area to restricttraveling, toward a side of the light exit surface, of light travelingtoward the outside of the illuminated area.

As described above, using the diverging portion, light travelingdirectly upward from the light emitting element is reduced while lighttraveling toward the periphery of the illuminated area is increased. Inaddition, the restricting portion is used to restrict traveling, towardthe side of the light exit surface outside of the illuminated area, of aluminous flux traveling from the inside toward the outside of theilluminated area. Accordingly, brightness non-uniformity in theilluminated area can be suppressed and a decline in contrast betweenilluminated areas caused by the incidence of a luminous flux of theilluminated area to another illuminated area can also be suppressed.

In the light guide plate described above, the restricting portionprovided on the light exit surface may be defined as a first restrictingportion, and a second restricting portion which opposes the firstrestricting portion may be provided on a surface on an opposite side ofthe light exit surface.

In the light guide plate described above, the diverging portion may be adepressed portion with a conical shape, a truncated cone shape, apyramid shape, a truncated pyramid shape, or a bowl shape, the depressedportion being provided on a surface on an opposite side of the lightexit surface and housing the light emitting element.

In the light guide plate described above, a plurality of diffusingportions which diffuse light may be provided on the light exit surface.

In the light guide plate described above, the restricting portion may bea groove provided on the light exit surface or a side surface of thelight guide plate.

In the light guide plate described above, a reflective layer whichreflects light may be provided in a portion, other than the divergingportion, of a surface on an opposite side of the light exit surface.

In the light guide plate described above, the diverging portion may be aprotruding portion with a conical shape, a truncated cone shape, apyramid shape, a truncated pyramid shape, or a bowl shape the protrudingportion being provided on a surface on an opposite side of the lightexit surface and being oriented toward the light emitting element.

In order to solve the problem described above, a planar light sourceapparatus according to the present invention includes:

a light emitting element; and

the light guide plate described above which guides light emitted fromthe light emitting element.

In addition, a planar light source apparatus according to the presentinvention includes a light emitting element, and a light guide platewhich guides light emitted from the light emitting element, the planarlight source apparatus further including: a diverging portion which is aprotruding portion with a conical shape, a truncated cone shape, apyramid shape, a truncated pyramid shape, or a bowl shape orientedtoward the light emitting element and provided on a surface on anopposite side of a light exit surface from which light is emitted fromthe light emitting element of the light guide plate, the divergingportion causing a luminous flux emitted from the light emitting elementto diverge; and a restricting portion which is a reflective surfaceprovided in a periphery of the light emitting element and which, when aprescribed range from the light emitting element on the light exitsurface is defined as an illuminated area illuminated by the lightemitting element, reflects light traveling from inside toward outside ofthe illuminated area to restrict traveling, toward a side of the lightexit surface, of light traveling toward the outside of the illuminatedarea.

Furthermore, the present invention may be provided as a displayapparatus including the planar light source apparatus described aboveand a display panel which receives light emitted from the planar lightsource apparatus and may be further provided as an electronic deviceincluding the display apparatus.

Advantageous Effects of Invention

According to the present invention, it is possible to provide atechnique for suppressing brightness non-uniformity of an areailluminated by a light source and also suppressing a decline in contrastbetween areas caused by incidence of a luminous flux of the area toanother area.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating a configuration of a liquidcrystal display apparatus.

FIG. 2 is a perspective view illustrating a configuration of a planarlight source apparatus.

FIG. 3 is a sectional view of a light guide plate.

FIG. 4 is an enlarged sectional view of a light guide plate.

FIG. 5 is a plan view showing a part of a light guide plate.

FIG. 6A is a plan view of a dot pattern.

FIG. 6B is a plan view of a dot pattern.

FIG. 7 is a diagram showing a direction of travel when light travelingfrom inside toward outside of the illuminated area is incident to agroove portion.

FIG. 8 is a sectional view schematically showing a second specificexample of a light guide plate.

FIG. 9 is a sectional view schematically showing a third specificexample of a light guide plate.

FIG. 10 is a sectional view showing a modification of a light guideplate according to the third specific example.

FIG. 11 is a sectional view schematically showing a fourth specificexample of a light guide plate.

FIG. 12 is a sectional view schematically showing a fifth specificexample of a light guide plate.

FIG. 13 is a sectional view schematically showing a sixth specificexample in which a transparent resin layer is arranged between a lightguide plate and a light source.

FIG. 14 is a diagram showing a first modification of the sixth specificexample.

FIG. 15 is a diagram showing a second modification of the sixth specificexample.

FIG. 16 is a sectional view schematically showing a seventh specificexample in which a transparent resin layer is arranged between a lightguide plate and a light source.

FIG. 17 is a sectional view schematically showing an eighth specificexample in which a transparent resin layer is arranged between a lightguide plate and a light source.

FIG. 18 is a sectional view schematically showing a ninth specificexample in which a transparent resin layer is arranged between a lightguide plate and a light source.

FIG. 19 is a sectional view schematically showing a tenth specificexample in which a transparent resin layer is arranged between a lightguide plate and a light source.

FIG. 20 is a sectional view schematically showing an eleventh specificexample in which a transparent resin layer is arranged between a lightguide plate and a light source.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings. It is to be understood that theembodiment described below merely represents examples of implementingthe present invention and are not intended to limit the presentinvention to the specific configurations described hereinafter.

In the embodiment described below, the “display apparatus” will bedescribed as a liquid crystal display apparatus and the “planar lightsource apparatus” will be described as a backlight of the liquid crystaldisplay apparatus.

(Configuration of Liquid Crystal Display Apparatus)

FIG. 1 is a perspective view illustrating a configuration of a liquidcrystal display apparatus according to the embodiment. As shown in FIG.1, the liquid crystal display apparatus includes: a planar light sourceapparatus 1 arranged as a backlight; and a display panel 2 whichreceives light emitted from the planar light source apparatus 1. Thedisplay panel 2 displays images by applying voltage to liquid crystalsencapsulated by being sandwiched between glass plates and increasing orreducing transmittance of light. Hereinafter, in the planar light sourceapparatus 1, a side of the display panel 2 may be described as an uppersurface side and a side of an opposite surface thereof may be describedas a lower surface side.

(Configuration of Planar Light Source Apparatus 1)

FIG. 2 is a perspective view illustrating a configuration of the planarlight source apparatus 1 according to the embodiment. The planar lightsource apparatus 1 includes a light guide plate 10 and a frame 12. Inaddition, the planar light source apparatus 1 includes a plurality oflight sources 11, a mounting substrate 13, and a reflective layer 14arranged on the lower surface side of the light guide plate 10. Thelower surface side of the light guide plate 10 is an opposite side of aside on which the display panel 2 is arranged. The planar light sourceapparatus 1 further includes a diffusing sheet 15, a prism sheet 16, anda light shielding member 17 laminated in order on the upper surface sideof the light guide plate 10. The upper surface side of the light guideplate 10 is the side on which the display panel 2 is arranged. One or aplurality of diffusing sheets 15 and prism sheets 16 may be provided orthe diffusing sheet 15 and the prism sheet 16 may be omitted.

The light guide plate 10 has an approximately flat plate shape and ismolded from a translucent material such as a polycarbonate resin or apolymethyl methacrylate resin. The light guide plate 10 need only have aplate shape along the display panel 2 and, when the display panel 2 iscurved, the light guide plate 10 desirably has a similarly curved plateshape. An upper surface of the light guide plate 10 is a light exitsurface from which light is emitted and which faces the display panel 2.The light guide plate 10 is configured such that light incident into thelight guide plate 10 is guided to the light exit surface and the entirelight exit surface is uniformly lighted.

The light source 11 is a light emitting element which receives supply ofpower and which emits white light from a light emitting surface. Whilethe light source 11 is, for example, an LED package, a light sourceother than an LED package may be used instead. The light source 11 isformed by encapsulating an LED chip that is a light emitting elementwith a translucent resin (resin layer) containing phosphor.Alternatively, instead of arranging the phosphor on the LED chip, aphosphor layer may be arranged on the light exit surface of the lightguide plate 10 or a phosphor layer may be arranged on the diffusingsheet 15. The light source 11 is driven by receiving supply of powerfrom the mounting substrate 13. A light source with a color other thanwhite may be used as the light source 11. The light source 11 isarranged below the light guide plate 10.

The frame 12 is a frame-like member (an example of a “frame body”) whichhas an opening and which is constituted by four sides. The frame 12 ismolded from a polycarbonate resin containing titanium oxide, apolycarbonate resin not containing titanium oxide, or the like. Thelight guide plate 10 is fitted into the frame 12, and an innercircumferential surface of the frame 12 surrounds a side surface of thelight guide plate 10 that forms an outer circumferential surface of thelight guide plate 10. The frame 12 has high reflectance and reflects andreuses light having leaked from the side surface of the light guideplate 10. The mounting substrate 13 is a substrate on which wiring isprovided by a conductive foil on an insulating substrate and which ismounted so that the light source 11 is electrically connected with thewiring.

The plurality of light sources 11 and the reflective layer 14 areprovided on the mounting substrate 13. The reflective layer 14 isprovided around the light sources 11. The reflective layer 14 is, forexample, a white resin, a metal foil, or the like with high reflectance,and reflects light traveling toward the lower surface side inside thelight guide plate 10 and returns the light to the side of the light exitsurface. The diffusing sheet 15 is a semi-transparent resin film whichdiffuses light emitted from the light exit surface of the light guideplate 10 and which widens directional characteristics of the light. Theprism sheet 16 is a transparent resin film which has a fine triangularprism-shaped pattern formed on an upper surface thereof and whichcollects light diffused by the diffusing sheet 15 and heightensbrightness when the planar light source apparatus 1 is viewed from theupper surface side.

The light shielding member 17 has a frame shape when the planar lightsource apparatus 1 is viewed from the upper surface side. The frameshape need only be a shape that surrounds the light guide plate 10 in asimilar manner to the upper surface of the frame 12 and may be, forexample, a rectangle shape, an approximately ellipsoidal shape, oranother shape. For example, the light shielding member 17 may be a blackadhesive tape in which both upper and lower faces are adhesive faces. Aframe portion of the light shielding member 17 is bonded along an upperend of the frame 12 and prevents light from leaking from the planarlight source apparatus 1.

First Specific Example

FIG. 3 is a sectional view of the light guide plate 10. A ratio of sizesof the respective components and the like are not limited to theillustrated example. The light guide plate 10 has a plurality ofdepressed portions 20 on the lower surface of the light guide plate 10.The depressed portion 20 has a conical shape. The plurality of lightsources 11 are arranged on the mounting substrate 13 and one lightsource 11 is housed inside each depressed portion 20. Light emitted fromthe light source 11 is incident into the light guide plate 10. Due tolight incident into the light guide plate 10 being refracted, reflected,and diffused inside the light guide plate 10 and emitted from a lightexit surface 1A of the light guide plate 10, the light exit surface 1Aof the light guide plate 10 is uniformly lighted. While a thickness(height) t1 of the light guide plate 10 is, for example, 0.35 mm, thethickness (height) t1 is not limited to this value and may assumeanother value such as 0.2 to 20 mm. While a pitch d1 of the lightsources 11 is, for example, 2 to 7 mm, the pitch d1 is not limited tothese values and may assume other values.

FIG. 4 is an enlarged sectional view of the light guide plate 10. Thelight guide plate 10 includes an incidence surface to which light fromthe light source 11 is incident, the light exit surface 1A which emitslight incident from the incidence surface, and a basal surface 1B on anopposite side of the light exit surface 1A. The basal surface 1B of thelight guide plate 10 constitutes the lower surface of the light guideplate 10. The depressed portion 20 is provided on the basal surface 1Bof the light guide plate 10. The depressed portion 20 with a conicalshape has an opening 21 and a tapered surface (an incidence surface) 23which narrows from the opening 21 toward a vertex 22. In other words, adiameter of the depressed portion 20 decreases upward from the opening21. The tapered surface 23 is a mirror surface or a smooth surfacesimilar to a mirror surface. A diameter of the opening 21 in thedepressed portion 20 and a height (depth) of the depressed portion 20are arbitrary values. Alternatively, the depressed portion 20 may have atruncated cone shape, a pyramid shape, a truncated pyramid shape, a bowlshape, a bell shape, or the like. In addition, a shape, a height, and awidth of the light source 11 are also not particularly limited. Forexample, the light source 11 may have a shape and a size which enable alight emitting surface of the light source 11 to be housed inside thedepressed portion 20.

A luminous flux emitted from the light source 11 is refracted anddiverged by the tapered surface 23 of the depressed portion 20. Thedepressed portion 20 is a mode of the diverging portion according to thepresent example.

In addition, a depressed portion 30 which is a conical depression in asimilar manner to the depressed portion 20 is provided at a positionopposing the depressed portion 20 on a side of the light exit surface ofthe light guide plate 10. A diameter of an opening of the depressedportion 30 and a height (depth) of the depressed portion 30 are alsoarbitrary values. Alternatively, the depressed portion 30 may have atruncated cone shape, a pyramid shape, a truncated pyramid shape, a bowlshape, a bell shape, or the like. The depressed portion 30 is a mode ofa diverging portion which causes a luminous flux emitted from the lightsource 11 to be refracted and diverged by a tapered surface 33. In thepresent example, when the depressed portion 20 is defined as a firstdiverging portion, the depressed portion 30 is a mode of a seconddiverging portion.

On the light exit surface 1A, a prescribed range centered on the lightsource 11 is defined as an illuminated area A0 illuminated by the lightsource 11, and a groove portion 50 is provided in a periphery of theilluminated area A0 on the light exit surface 1A. The groove portion 50has a V-shaped cross section and includes an opening 51 and inclinedsurfaces 53 of which a space therebetween narrows from the opening 51toward a lower end 52. A width of the opening 51 in the groove portion50 and a height (depth) of the groove portion 50 are arbitrary values.The groove portion 50 is a restricting portion which deflects lighttraveling from inside toward outside of the illuminated area A0 torestrict traveling, toward a side of the light exit surface, of lighttraveling toward the outside of the illuminated area A0. In the presentembodiment, deflection refers to changing an orientation (direction oftravel) of light by an optical effect such as refraction, reflection, ordiffraction. The illuminated area A0 represents a unit of a region inwhich brightness is adjusted when performing local dimming. As shown inFIG. 3, a width (length) of the illuminated area A0 according to thepresent example is the same as a pitch d1 between light sources 11 in adirection of arrangement of the light sources 11.

In addition, a groove portion 60 which is a depression with a V-shapedcross section in a similar manner to the groove portion 50 is providedat a position opposing the groove portion 50 on the side of the lightexit surface of the light guide plate 10. The groove portion 60 has aV-shaped cross section and includes an opening 61 and inclined surfaces63 of which a space therebetween narrows from the opening 61 toward anupper end 62. A width of the opening 61 and a height (depth) of thegroove portion 60 are arbitrary values. The groove portion 60 is arestricting portion which deflects light traveling from the insidetoward the outside of the illuminated area A0 to restrict traveling,toward a side of the light exit surface, of light traveling toward theoutside of the illuminated area A0. In the present example, when thegroove portion 50 is defined as a first restricting portion, the grooveportion 60 is a second restricting portion.

FIG. 5 is a plan view showing apart of the light guide plate 10. In thelight guide plate 10, a square range centered on each of the lightsources 11 arranged in a matrix pattern is defined as the illuminatedarea A0 illuminated by each light source 11, and the groove portion 50is vertically and horizontally provided along the periphery of theilluminated area A0. Moreover, although not illustrated, the grooveportion 60 is also vertically and horizontally provided on the basalsurface B of the light guide plate 10 in a similar manner to the grooveportion 50 shown in FIG. 5. A planar shape of the illuminated area A0provided with the groove portion 50 in the periphery thereof may beother shapes. Any shape capable of tessellating a plane such as arectangle or a hexagon may be adopted.

On the light exit surface 1A of the light guide plate 10, a plurality ofdot patterns 41 are provided in a portion other than the depressedportion 30 and the groove portion 50. In addition, on the basal surface1B of the light guide plate 10, a plurality of dot patterns 42 areprovided in a portion other than the depressed portion 20 and the grooveportion 60. The light inside the light guide plate 10 is refracted anddiffused by the dot patterns 41 provided on the light exit surface 1A ofthe light guide plate 10 and the dot patterns 42 provided on the basalsurface 1B of the light guide plate 10. The dot patterns 41 and 42 areexamples of the diffusing portion.

While the dot patterns 41 shown in FIG. 4 have a projection shape(convex shape) that projects toward the outside of the light guide plate10, the dot patterns 41 are not limited to this shape and may have aconcave shape that is depressed toward the inside of the light guideplate 10. While the dot patterns 42 shown in FIG. 4 have a concave shapethat is depressed toward the inside of the light guide plate 10, the dotpatterns 42 are not limited to this shape and may have a projectionshape (convex shape) that projects toward the outside of the light guideplate 10. Examples of the projection shape include a convex lens shape,a columnar shape, a prismatic shape, a conical shape, and a pyramidshape. Examples of the concave shape include a concave lens shape, acolumnar groove shape, a prismatic groove shape, a conical groove shape,and a pyramid groove shape. The dot patterns 41 and 42 may be any of acircle, an ellipse, and a polygon in a plan view. The dot patterns 41and 42 may be integrally formed with the light guide plate 10 when thelight guide plate 10 is manufactured by injection molding.Alternatively, the dot patterns 41 and 42 may be separately formed onthe light guide plate 10 by an ink-jet or the like. The dot patterns 41and 42 may have minute irregularities on surfaces thereof. Formingminute irregularities on the surfaces of the dot patterns 41 and 42enables light incident to the dot patterns 41 and 42 to be furtherdiffused.

The plurality of dot patterns 41 and 42 are respectively denselyarranged. While the plurality of dot patterns 41 and 42 may bediscretely arranged, in order to enhance an effect of diffusing lightinside the light guide plate 10 and light emitted from the light exitsurface 1A of the light guide plate 10 so that the light becomesuniform, the plurality of dot patterns 41 and 42 are preferably denselyarranged. For example, as shown in FIG. 6A, the plurality of dotpatterns 41 may be arranged in a closest-packed arrangement. FIG. 6A isa plan view of the dot patterns 41 as viewed from a normal direction ofthe light exit surface 1A of the light guide plate 10. The dot patterns41 shown in FIG. 6A have a hexagonal shape in a plan view and theplurality of the dot patterns 41 are arranged adjacent to each other.Alternatively, for example, the plurality of dot patterns 41 may bearranged as shown in FIG. 6B. FIG. 6B is a plan view of the dot patterns41 as viewed from a normal direction of the light exit surface 1A of thelight guide plate 10. The dot patterns 41 shown in FIG. 6B have acircular shape in a plan view and the plurality of the dot patterns 41are arranged adjacent to each other. While a width of the dot patterns41 and 42 is, for example, 30 □m and a height of the dot patterns 41 and42 is, for example, 5 to 6 □m, the width and the height of the dotpatterns 41 and 42 are not limited to these values and may assume othervalues.

The dot patterns 41 and 42 may have a same size (height and width) ormay respectively have different sizes. The dot patterns 41 and the dotpatterns 42 may have a same size or the dot patterns 41 and the dotpatterns 42 may have different sizes. The sizes of the dot patterns 41and 42 may be changed in accordance with a value of the thickness of thelight guide plate 10 and a value of the pitch between adjacent lightsources 11.

As shown in FIG. 4, the light guide plate 10 according to the presentexample includes the depressed portions 20 and 30 above the light source11 and causes a luminous flux traveling upward from the light source 11to diverge. Accordingly, light traveling directly upward from the lightsource 11 is reduced while light traveling toward the periphery of theilluminated area A0 is increased. In addition, light traveling towardthe periphery of the illuminated area A0 and light reflected inside thelight guide plate 10 are diffused by the diffusing portions 41 and 42.Accordingly, brightness on the light exit surface 1A is made uniform.

In addition, the light guide plate 10 according to the present exampleincludes groove portions 50 and 60 along the periphery of theilluminated area A0. Accordingly, light traveling from the inside towardthe outside of the illuminated area A0 is deflected to restricttraveling, toward the side of the light exit surface, of light travelingtoward the outside of the illuminated area A0. FIG. 7 is a diagramshowing a direction of travel when light traveling from the insidetoward the outside of the illuminated area A0 is incident to the grooveportion 50. As shown in FIG. 7, when light 99 traveling from the insidetoward the outside of the illuminated area A0 reaches the groove portion50, when an angle of incidence with respect to the inclined surface 53is equal to or larger than a critical angle, the light 99 is subjectedto total reflection and returns to the inside of the illuminated area A0as indicated by light 98. Since emission from the light exit surface 1Aoutside of the illuminated area A0 of the light source 11 by lightemitted from the light source 11 is suppressed, a decline in contrastbetween illuminated areas when performing local dimming can besuppressed.

Second Specific Example

FIG. 8 is a sectional view schematically showing a second specificexample of the light guide plate 10. In the present specific example,components corresponding to the configuration described above will beassigned corresponding reference numerals and a description thereof willbe omitted.

The light guide plate 10 according to the present specific example isconfigured so as to be formed by an individual piece for each lightsource 11 and arranged in a matrix pattern corresponding to the lightsources 11.

The first restricting portion according to the present second specificexample is constituted by a side surface 71 of the light guide plate 10formed as an individual piece. For example, by installing individualpieces of the light guide plate 10 in a row while providing minute gapsbetween the side surfaces 71 and reflecting light incident to the sidesurface 71 at angles exceeding the critical angle, traveling, toward theside of the light exit surface outside the illuminated area A0, of lighttraveling from the inside toward the outside of the illuminated area A0is restricted. In addition to a configuration in which gaps are providedbetween the side surfaces 71, light traveling from the inside toward theoutside of the illuminated area A0 can be shielded or reflected byapplying a light shielding coating material or forming a reflectivelayer on the side surface 71.

In addition, a notched portion 79 constituted by an inclined surface 72and a surface 73 parallel to the basal surface 1B is provided on theside of the basal surface 1B of the side surface 71, and when theindividual pieces of the light guide plate 10 are arranged in a row, thenotched portion 79 constitutes the second restricting portion in asimilar manner to the groove portion 60 shown in FIG. 4.

Even in the configuration shown in FIG. 8, due to the depressed portion20 provided above the light source 11, light traveling directly upwardfrom the light source 11 is reduced while light traveling toward theperiphery of the illuminated area A0 is increased. In addition, the sidesurface 71 that is the first restricting portion and the notched portion79 that is the second restricting portion are used to restricttraveling, toward the side of the light exit surface outside of theilluminated area A0, of a luminous flux traveling from the inside towardthe outside of the illuminated area A0.

Accordingly, brightness non-uniformity in the illuminated area A0 thatis illuminated by the light source 11 can be suppressed and a decline incontrast between illuminated areas caused by the incidence of a luminousflux of the illuminated area A0 to another illuminated area can also besuppressed.

Although not illustrated in FIG. 8, even in the light guide plate 10according to the present example, the dot patterns 41 and the depressedportion 30 (the second diverging portion) may be provided on the lightexit surface 1A in a similar manner to FIG. 4. In addition, the dotpatterns 42 may be provided in a portion, other than the depressedportion 20 and the notched portion 79, of the basal surface 1B in asimilar manner to FIG. 4.

Third Specific Example

FIG. 9 is a sectional view schematically showing a third specificexample of the light guide plate 10. In the present third specificexample, components corresponding to the configurations described abovewill be assigned corresponding reference numerals and a descriptionthereof will be omitted.

As shown in FIG. 9, in the present third specific example, a reflectivelayer 81 is formed on an inner surface of the groove portion 60. Byforming a reflective surface on the inclined surface 63 of the grooveportion 60 in this manner, light traveling from the inside toward theoutside of the illuminated area A0 is reflected toward the inside of theilluminated area A0 when striking the groove portion 60. Thisconfiguration restricts traveling, toward the side of the light exitsurface outside of the illuminated area A0, of light traveling from theinside toward the outside of the illuminated area A0.

In addition, FIG. 10 is a diagram showing a modification of the lightguide plate 10 described above. While only the depressed portion 20 andthe groove portion 60 are shown on the basal surface 1B of the lightguide plate 10 in FIG. 9, as shown in FIG. 10, the basal surface 1B ofthe light guide plate 10 may include a flat portion 65 between thedepressed portion 20 and the groove portion 60 and the reflective layer81 may also be provided in the flat portion 65.

Even in the configuration shown in FIG. 9, due to the depressed portion20 provided above the light source 11, light traveling directly upwardfrom the light source 11 is reduced while light traveling toward theperiphery of the illuminated area A0 is increased. In addition, thegroove portion 50 that is the first restricting portion and the grooveportion 60 that is the second restricting portion are used to restricttraveling, toward the side of the light exit surface outside of theilluminated area A0, of light traveling from the inside toward theoutside of the illuminated area A0.

Accordingly, brightness non-uniformity in the illuminated area A0 thatis illuminated by the light source 11 can be suppressed and a decline incontrast between illuminated areas caused by the incidence of a luminousflux of the illuminated area A0 to another illuminated area can also besuppressed.

Although not illustrated in FIG. 10, even in the light guide plate 10according to the present example, the dot patterns 41 and the depressedportion 30 (the second diverging portion) may be provided on the lightexit surface 1A in a similar manner to FIG. 4. In addition, the dotpatterns 42 may be provided in the flat portion 65 of the basal surface1B in a similar manner to FIG. 4.

Fourth Specific Example

FIG. 11 is a sectional view schematically showing a fourth specificexample of the light guide plate 10. In the present fourth specificexample, components corresponding to the configurations described abovewill be assigned corresponding reference numerals and a descriptionthereof will be omitted.

As shown in FIG. 11, in the present fourth specific example, a conicalprotruding portion 90 provided on the basal surface 1B toward a lightemitting element is provided. The protruding portion 90 is a mode of thediverging portion. The protruding portion 90 has a conical shape andincludes a circular bottom surface 91 and a tapered surface 93 whichtapers from the bottom surface 91 toward a vertex 92.

The tapered surface 93 is a mirror surface or a smooth surface similarto a mirror surface. A diameter of the bottom surface 91 in theprotruding portion 90 and a height (depth) of the protruding portion 90are arbitrary values. Alternatively, the protruding portion 90 may havea truncated cone shape, a pyramid shape, a truncated pyramid shape, abowl shape, a bell shape, or the like. A luminous flux emitted from thelight source 11 is refracted and diverged by the tapered surface 93 ofthe protruding portion 90.

Even in the configuration shown in FIG. 11, the protruding portion 90provided above the light source 11 causes a luminous flux emitted fromthe light source 11 to diverge so as to reduce light traveling directlyupward while increasing light traveling toward the periphery of theilluminated area A0. In addition, the groove portion 50 that is arestricting portion is used to restrict traveling, toward the side ofthe light exit surface outside of the illuminated area A0, of lighttraveling from the inside toward the outside of the illuminated area A0.

Accordingly, brightness non-uniformity in the illuminated area A0 thatis illuminated by the light source 11 can be suppressed and a decline incontrast between illuminated areas caused by the incidence of a luminousflux of the illuminated area A0 to another illuminated area can also besuppressed.

Although not illustrated in FIG. 11, even in the light guide plate 10according to the present example, the dot patterns 41 and the depressedportion 30 (the second diverging portion) may be provided on the lightexit surface 1A in a similar manner to FIG. 4. In addition, the dotpatterns 42 may be provided in the flat portion 65 of the basal surface1B in a similar manner to FIG. 4.

Fifth Specific Example

FIG. 12 is a sectional view schematically showing a fifth specificexample in which a diverging portion is provided in the light guideplate 10 and a restricting portion is provided on a mounting substrate.In the present fifth specific example, components corresponding to theconfigurations described above will be assigned corresponding referencenumerals and a description thereof will be omitted.

As shown in FIG. 12, in the present fifth specific example, the conicalprotruding portion 90 provided on the basal surface 1B toward a lightemitting element is used as a diverging portion. The protruding portion90 has a conical shape and includes the circular bottom surface 91 andthe tapered surface 93 which tapers from the bottom surface 91 towardthe vertex 92.

The tapered surface 93 is a mirror surface or a smooth surface similarto a mirror surface. A diameter of the bottom surface 91 in theprotruding portion 90 and a height (depth) of the protruding portion 90are arbitrary values. Alternatively, the protruding portion 90 may havea truncated cone shape, a pyramid shape, a truncated pyramid shape, abowl shape, a bell shape, or the like. A luminous flux emitted from thelight source 11 is refracted and diverged by the tapered surface 93 ofthe protruding portion 90.

In addition, a reflecting portion 95 is provided in a periphery of thelight source 11 on the mounting substrate 13 which is a mounting surfaceof the light source 11. The reflecting portion 95 has a V-shaped crosssection that protrudes upward from the mounting substrate 13 and has alinear shape in a plan view. The reflecting portion 95 is provided in alattice pattern along the periphery of the illuminated area AD in asimilar manner to the groove portion 50 shown in FIG. 5.

As described above, the reflecting portion 95 is provided in theperiphery of the illuminated area A0, and when light traveling from theinside toward the outside of the illuminated area A0 strikes thereflecting portion 95, the light is reflected toward the inside of theilluminated area A0. This configuration restricts traveling, toward theside of the light exit surface outside of the illuminated area A0, oflight traveling from the inside toward the outside of the illuminatedarea A0. In the present fifth specific example, the reflecting portion95 is a mode of the restricting portion.

Even in the configuration shown in FIG. 12, the protruding portion 90provided above the light source 11 causes a luminous flux emitted fromthe light source 11 to diverge so as to reduce light traveling directlyupward while increasing light traveling toward the periphery of theilluminated area A0. In addition, the reflecting portion 95 that is arestricting portion is used to restrict traveling, toward the side ofthe light exit surface outside of the illuminated area A, of lighttraveling from the inside toward the outside of the illuminated area A.

Accordingly, brightness non-uniformity in the illuminated area AU thatis illuminated by the light source 11 can be suppressed and a decline incontrast between illuminated areas caused by the incidence of a luminousflux of the illuminated area A0 to another illuminated area can also besuppressed.

Although not illustrated in FIG. 12, even in the light guide plate 10according to the present example, the dot patterns 41 and the depressedportion 30 (the second diverging portion) may be provided on the lightexit surface 1A in a similar manner to FIG. 4.

Sixth Specific Example

FIG. 13 is a sectional view schematically showing a sixth specificexample of the planar light source apparatus 1 in which a transparentresin layer 59 is arranged between the light guide plate 10 and thelight source 11. In the present sixth specific example, componentscorresponding to the configurations described above will be assignedcorresponding reference numerals and a description thereof will beomitted.

In the sixth specific example shown in FIG. 13, the transparent resinlayer 59 is arranged between the light guide plate 10 and the pluralityof light sources 11 and the reflective layer 14. In particular, in thepresent sixth specific example, the plurality of light sources 11 areembedded in the transparent resin layer 59, and a light emitting portionof each light source 11 is covered by the transparent resin layer 59.While the light source 11 is not housed inside the depressed portion 20of the light guide plate 10 in the present sixth specific example, thelight source 11 is arranged below the depressed portion 20 and a centerof the light emitting portion of the light source 11 and a center of thedepressed portion 20 coincide with each other. In this case, thecoincidence of the centers with each other is not limited to the centersprecisely coinciding with each other and may include cases where, forexample, the center of the light emitting portion of the light source 11is positioned within a prescribed range with respect to the center ofthe depressed portion (for example, 10% of a width of the depressedportion).

Light emitted from the light source 11 passes through the transparentresin layer 59 and is made incident into the light guide plate 10. Atthis point, a luminous flux traveling toward directly above the lightsource 11 travels while spreading inside the transparent resin layer 59and is refracted and further diffused when emitted into the depressedportion 20 of the light guide plate 10 from the upper surface. Byproviding the transparent resin layer 59 between the light guide plate10 and the light source 11 in this manner, diffusion of a luminous fluxtraveling directly upward from the light source 11 is promoted andbrightness inside the illuminated area A0 can be made further uniform.In addition, light which is reflected by the reflective layer 14 andwhich returns to the light guide plate 10 via the transparent resinlayer 59 is also further diffused inside the transparent resin layer 59and contributes to making brightness uniform. A thickness of thetransparent resin layer 59 can be arbitrarily set and, for example, byincreasing the thickness of the transparent resin layer 59 (making thetransparent resin layer 59 thicker), a distance between the light source11 and the light guide plate 10 can be increased. Since increasing thedistance between the light source 11 and the light guide plate 10enables an effect of making brightness uniform to be enhanced, thethickness of the transparent resin layer 59 may be set such that, whilesecuring a distance necessary for making brightness uniform, thedistance is minimized.

FIG. 14 is a diagram showing a first modification of the sixth specificexample. While FIG. 13 shows an example of using the light guide plate10 shown in FIG. 8, the planar light source apparatus 1 according to thesixth specific example is not limited thereto and may be configured sothat the light guide plate 10 shown in FIG. 4, 9, or 10 is adopted andthe transparent resin layer 59 is arranged between the light guide plate10 and the light source 11. FIG. 14 shows an example of using the lightguide plate 10 shown in FIG. 4.

FIG. 15 is a diagram showing a second modification of the sixth specificexample. While the upper surface of the transparent resin layer 59 isconfigured as a flat surface in FIG. 13, in the transparent resin layer59 according to the second modification shown in FIG. 15, a protrudingportion 591 which protrudes upward (toward a side of the depressedportion 20 of the light guide plate 10) is provided in a portionpositioned below the depressed portion 20. While the protruding portion591 has a hemispherical shape, alternatively, the protruding portion 591may have a projection shape (convex shape) such as a columnar shape, aprismatic shape, a conical shape, or a pyramid shape.

Seventh Specific Example

FIG. 16 is a sectional view schematically showing a seventh specificexample of the planar light source apparatus 1 in which a transparentresin layer 58 is arranged between the light guide plate 10 and thelight source 11. In the present seventh specific example, componentscorresponding to the configurations described above will be assignedcorresponding reference numerals and a description thereof will beomitted.

In the seventh specific example shown in FIG. 16, the transparent resinlayer 58 is arranged below the light guide plate 10 and around each ofthe plurality of light sources 11. Therefore, each light source 11 isembedded in each transparent resin layer 58 and a light emitting portionof the light source 11 is covered by a transparent resin layer 57. Inthe present seventh specific example, the light source 11 is not housedinside the depressed portion 20 of the light guide plate 10. While thetransparent resin layer 58 shown in FIG. 16 has an approximatelyhemispherical shape, the transparent resin layer 58 is not limited tothis shape and may have a projection shape (convex shape) such as acolumnar shape, a prismatic shape, a conical shape, or a pyramid shape.A part of the transparent resin layer 58 may be positioned inside thedepressed portion 20 of the light guide plate 10 or the transparentresin layer 58 may not be positioned inside the depressed portion 20 ofthe light guide plate 10. Light emitted from the light source 11 passesthrough the transparent resin layer 58 and is made incident into thelight guide plate 10.

In addition, in the present seventh specific example, a gap 18 isprovided between the basal surface 1B of the light guide plate 10 andthe reflective layer 14 by causing a part of an upper surface of thetransparent resin layer 58 formed in a projection shape to abut againstthe basal surface 1B of the light guide plate 10. A distance L1 betweenthe basal surface 1B and the reflective layer 14 can be arbitrarily setin accordance with a height of the transparent resin layer 58. Theplanar light source apparatus 1 according to the present seventhspecific example may be configured so that the light guide plate 10shown in FIG. 4, 9, or 10 is adopted in place of the light guide plate10 shown in FIG. 16 and the transparent resin layer 58 is arrangedbetween the light guide plate 10 and the light source 11.

Eighth Specific Example

FIG. 17 is a sectional view schematically showing an eighth specificexample of the planar light source apparatus 1 in which a transparentresin layer 57 is arranged between the light guide plate 10 and thelight source 11. In the present eighth specific example, componentscorresponding to the configurations described above will be assignedcorresponding reference numerals and a description thereof will beomitted.

In the eighth specific example shown in FIG. 17, the transparent resinlayer 57 is arranged below the light guide plate 10 and around each ofthe plurality of light sources 11. Therefore, each light source 11 isembedded in each transparent resin layer 57 and a light emitting portionof the light source 11 is covered by the transparent resin layer 57. Inthe present eighth specific example, the light source 11 is not housedinside the depressed portion 20 of the light guide plate 10. Thetransparent resin layer 57 shown in FIG. 17 has an upward-convexprojection shape that is, for example, a shape in which twoapproximately hemispherical shapes are connected to each other or adonut shape which is depressed at a center in a plan view but aperiphery of the depression protrudes upward in an annular belt shape. Apart of the transparent resin layer 57 may be positioned inside thedepressed portion 20 of the light guide plate 10 or the transparentresin layer 57 may not be positioned inside the depressed portion 20 ofthe light guide plate 10. Light emitted from the light source 11 passesthrough the transparent resin layer 57 and is made incident into thelight guide plate 10.

In addition, in the present eighth specific example, the gap 18 isprovided between the basal surface 1B of the light guide plate 10 andthe reflective layer 14 by causing a part of an upper surface of thetransparent resin layer 57 formed in a projection shape to abut againstthe basal surface 1B of the light guide plate 10. A distance L1 betweenthe basal surface 1B and the reflective layer 14 can be arbitrarily setin accordance with a height of the transparent resin layer 57. Theplanar light source apparatus 1 according to the present eighth specificexample may be configured so that the light guide plate 10 shown in FIG.4, 9, or 10 is adopted in place of the light guide plate 10 shown inFIG. 17 and the transparent resin layer 57 is arranged between the lightguide plate 10 and the light source 11.

Ninth Specific Example

FIG. 18 is a sectional view schematically showing a ninth specificexample of the planar light source apparatus 1 in which a transparentresin layer 56 is arranged between the light guide plate 10 and thelight source 11. In the present ninth specific example, componentscorresponding to the configurations described above will be assignedcorresponding reference numerals and a description thereof will beomitted.

In the ninth specific example shown in FIG. 18, a plurality oftransparent resin layers 56 are arranged below the light guide plate 10and the transparent resin layer 56 is arranged between the light guideplate 10 and each of the plurality of light sources 11. Therefore, eachlight source 11 is embedded in each transparent resin layer 56 and alight emitting portion of the light source 11 is covered by thetransparent resin layer 56. In the present ninth specific example, thelight source 11 and the transparent resin layer 56 are housed inside thedepressed portion 20 of the light guide plate 10 and the basal surface1B of the light guide plate 10 and the reflective layer 14 are incontact with each other. In other words, the light guide plate 10 andthe reflective layer 14 are in close contact with each other. The bottomsurface (opening) 21 of the depressed portion 20 of the light guideplate 10 and the transparent resin layer 56 may be in contact with eachother or the bottom surface 21 of the depressed portion 20 of the lightguide plate 10 and the transparent resin layer 56 may not be in contactwith each other. The tapered surface 23 of the depressed portion 20 ofthe light guide plate 10 and the transparent resin layer 56 may be incontact with each other or the tapered surface 23 of the depressedportion 20 of the light guide plate 10 and the transparent resin layer56 may not be in contact with each other. While the transparent resinlayer 56 shown in FIG. 18 has an approximately hemispherical shape, thetransparent resin layer 56 is not limited to this shape and may have aprojection shape (convex shape) such as a columnar shape, a prismaticshape, a conical shape, or a pyramid shape. Light emitted from the lightsource 11 passes through the transparent resin layer 56 and is madeincident into the light guide plate 10. The planar light sourceapparatus 1 according to the present ninth specific example may beconfigured so that the light guide plate 10 shown in FIG. 4, 9, or 10 isadopted in place of the light guide plate 10 shown in FIG. 18 and thetransparent resin layer 56 is arranged between the light guide plate 10and the light source 11.

Tenth Specific Example

FIG. 19 is a sectional view schematically showing a tenth specificexample of the planar light source apparatus 1 in which a transparentresin layer 55 is arranged between the light guide plate 10 and thelight source 11. In the present tenth specific example, componentscorresponding to the configurations described above will be assignedcorresponding reference numerals and a description thereof will beomitted.

In the tenth specific example shown in FIG. 19, a plurality oftransparent resin layers 55 are arranged below the light guide plate 10and the transparent resin layer 55 is arranged between the light guideplate 10 and each of the plurality of light sources 11. Therefore, eachlight source 11 is embedded in each transparent resin layer 55 and alight emitting portion of the light source 11 is covered by thetransparent resin layer 55. In the present tenth specific example, thelight source 11 and the transparent resin layer 55 are housed inside thedepressed portion 20 of the light guide plate 10. The basal surface 1Bof the light guide plate 10 and the reflective layer 14 are in contactwith each other. In other words, the light guide plate 10 and thereflective layer 14 are in close contact with each other. The bottomsurface 21 of the depressed portion 20 of the light guide plate 10 andthe transparent resin layer 55 may be in contact with each other or thebottom surface 21 of the depressed portion 20 of the light guide plate10 and the transparent resin layer 55 may not be in contact with eachother. The tapered surface 23 of the depressed portion 20 of the lightguide plate 10 and the transparent resin layer 55 may be in contact witheach other or the tapered surface 23 of the depressed portion 20 of thelight guide plate 10 and the transparent resin layer 55 may not be incontact with each other. The transparent resin layer 55 has anupward-convex projection shape that is, for example, a shape in whichtwo approximately hemispherical shapes are connected to each other or adonut shape which is depressed at a center in a plan view but aperiphery of the depression protrudes upward in an annular belt shape.Light emitted from the light source 11 passes through the transparentresin layer 55 and is made incident into the light guide plate 10. Theplanar light source apparatus 1 according to the present tenth specificexample may be configured so that the light guide plate 10 shown in FIG.4, 9, or 10 is adopted in place of the light guide plate 10 shown inFIG. 19 and the transparent resin layer 55 is arranged between the lightguide plate 10 and the light source 11.

Eleventh Specific Example

FIG. 20 is a sectional view schematically showing an eleventh specificexample of the planar light source apparatus 1 in which a transparentresin layer 54 is arranged between the light guide plate 10 and thelight source 11. In the present eleventh specific example, componentscorresponding to the configurations described above will be assignedcorresponding reference numerals and a description thereof will beomitted.

In the eleventh specific example shown in FIG. 20, a plurality oftransparent resin layers 54 are arranged below the light guide plate 10and the transparent resin layer 54 is arranged between the light guideplate 10 and each of the plurality of light sources 11. Therefore, eachlight source 11 is embedded in each transparent resin layer 54 and alight emitting portion of the light source 11 is covered by thetransparent resin layer 54. In the present eleventh specific example,the basal surface 1B of the light guide plate 10 and the reflectivelayer 14 are held at a prescribed distance by a spacer (not illustrated)and the light guide plate 10 and the reflective layer 14 are separatedfrom each other. A vertex (lower portion) of the protruding portion 90of the light guide plate 10 and the transparent resin layer 54 may be incontact with each other or the vertex (lower portion) of the protrudingportion 90 of the light guide plate 10 and the transparent resin layer54 may not be in contact with each other.

The transparent resin layer 54 has an upward-convex projection shapethat is, for example, a shape in which two approximately hemisphericalshapes are connected to each other or a donut shape which is depressedat a center in a plan view but a periphery of the depression protrudesupward in an annular belt shape. Alternatively, the transparent resinlayer 54 may have a hemispherical shape as in the case of thetransparent resin layer 56 shown in FIG. 18. Light emitted from thelight source 11 passes through the transparent resin layer 54 and ismade incident into the light guide plate 10.

In the specific examples shown in FIGS. 13 to 17, the light sources 11and the depressed portions 20 of the light guide plate 10 overlap withone another and the light sources 11 are arranged below the depressedportions 20 of the light guide plate 10 when viewed from a normaldirection of the light exit surface 1A of the light guide plate 10. Byarranging any of the transparent resin layers 57 to 59 between the lightguide plate 10 and the light sources 11, a distance between the lightguide plate 10 and the light sources 11 can be kept constant withoutincreasing the thickness of the light guide plate 10. By separating thelight guide plate 10 and the light sources 11 from each other withouthousing the light sources 11 inside the depressed portions 20 of thelight guide plate 10, a spread of light incident into the light guideplate 10 can be increased. Thicknesses of the transparent resin layers57 to 59 are arbitrary. By changing the thicknesses of the transparentresin layers 57 to 59, the distance between the light guide plate 10 andthe light sources 11 can be changed. For example, by changing thethicknesses of the transparent resin layers 57 to 59 in accordance witha type of the light sources 11, the distance between the light guideplate 10 and the light sources 11 can be changed in accordance with thetype of the light sources 11.

In the specific examples shown in FIGS. 18 to 20, the light sources 11and the depressed portions 20 of the light guide plate 10 overlap withone another and the light sources 11 are arranged below the depressedportions 20 of the light guide plate 10 when viewed from a normaldirection of the light exit surface 1A of the light guide plate 10.Accordingly, a luminous flux emitted from the light sources 11 is causedto diverge by the upper surface of the transparent resin layers 54 to 56and a spread of light incident into the light guide plate 10 widens.Thicknesses of the transparent resin layers 54 to 56 are arbitrary. Forexample, the thicknesses of the transparent resin layers 54 to 56 may bechanged in accordance with the type of the light sources 11.

A display apparatus including the light guide plate 10 described in thefirst to fifth specific examples of the embodiment described above canbe mounted to various electronic devices. Examples of electronic devicesprovided with such a display apparatus include a smartphone, a digitalcamera, a tablet terminal, an electronic book, a wearable device, a carnavigation apparatus, an electronic dictionary, and an electronicbillboard. Using the light guide plate and the display apparatusaccording to the embodiment enables brightness non-uniformity ofelectronic devices to be reduced while reducing sizes and thicknesses ofthe electronic devices.

REFERENCE SIGNS LIST

-   1 Planar light source apparatus-   1A Light exit surface-   1B Basal surface-   2 Display panel-   10 Light guide plate-   11 Light source-   12 Frame-   13 Mounting substrate-   14 Reflective layer-   15 Diffusing sheet-   16 Prism sheet-   17 Light shielding member-   20,30 Depressed portion-   21 Opening-   22 Vertex-   23 Tapered surface-   30 Depressed portion-   41,42 Dot pattern-   54 to 59 Transparent resin layer

The invention claimed is:
 1. A planar light source apparatus,comprising: a plurality of light sources provided in a matrix pattern;and a light guide plate, provided over the plurality of light sources,comprising a plurality of pieces respectively corresponding to each ofthe plurality of light sources, wherein: the plurality of pieces arearranged such that a gap between side surfaces of each of the pluralityof pieces is formed, each of the plurality of pieces comprise a lightexit surface that emits light emitted from the light source, a lowersurface provided on an opposite side of the piece from the light exitsurface, and the side surface, which faces an adjacent one of thepieces, the side surfaces of each of the pieces comprise: a first sidesurface provided on a light exit surface side of the side surface; and asecond side surface provided on a lower surface side of the sidesurface, each of the gaps comprise a first gap between the respectivefirst side surfaces and a second gap between the respective second sidesurfaces, and the second gap is larger than the first gap.
 2. The planarlight source apparatus according to claim 1, wherein a reflective layerwhich reflects the light emitted from the light source is provided oneach of the second side surfaces.
 3. The planar light source apparatusaccording to claim 2, wherein each of the plurality of pieces include aflat portion on the lower surface, and a reflective layer which reflectsthe light emitted from the light source is provided on the flat portion.4. The planar light source apparatus according to claim 1, furthercomprising a mounting substrate provided on the lower surface side ofthe light guide plate, and a reflective layer which reflects the lightemitted from the light source provided on the mounting substrate.
 5. Theplanar light source apparatus according to claim 4, wherein theplurality of light sources are provided on the mounting substrate, andthe reflective layer which reflects the light emitted from the lightsource is provided in a periphery of the light source.
 6. The planarlight source apparatus according to claim 1, further comprising atransparent resin layer that covers the light source.
 7. The planarlight source apparatus according to claim 6, wherein the transparentresin layer comprises a shape, which is depressed at a center in a planview.
 8. The planar light source apparatus according to claim 1, whereina plurality of dot patterns that diffuse the light emitted from thelight exit surface is provided on the light exit surface of each of theplurality of pieces.
 9. A display apparatus, comprising: the planarlight source apparatus according to claim 1; and a display panel, whichreceives light emitted from the planar light source apparatus.
 10. Anelectronic device comprising the display apparatus according to claim 9.